Blockchain technology was developed as a way of providing a publicly transparent and decentralized ledger that is configured to track and store digital transactions in a publicly verifiable, secure, and hardened manner to prevent tampering or revision.
A typical blockchain includes three primary functions: read, write, and validate. For example, a user of the blockchain must have the ability to read the data that resides on the blockchain. A user of the blockchain must also have the ability to write, e.g. append, data to the blockchain. Every write operation starts out as a proposed transaction that is posted on the network. The proposed transaction may not always be valid, for example, it may be malformed (syntax errors), or it may constitute an attempt to perform a task for which the submitter is not authorized. Validation refers to filtering out invalid transactions and then deciding on the exact order for the remaining, valid, transactions to be appended to the blockchain. This process is often called consensus. During consensus, validator nodes of the blockchain may vote on whether each submitted transaction is valid and the order in which to add the transactions to the blockchain.
Once ordered, the transactions are packaged into blocks which are in turn appended to the blockchain. Each new block that is appended to the blockchain also includes a hash of the previous block. Accordingly, as each new block is added, the security and integrity of the entire blockchain is further enhanced. It is important to note that once data is written to the blockchain, for example, once a block including transactions has been appended to the blockchain, that data can no longer be altered or modified. In a typical blockchain, the anonymity of the users is protected through the use of pseudonyms and the transaction data itself is protected through the use of cryptography, e.g., via the use of hash codes.